(a) Technical Field
The present disclosure relates to a fail-safe method and apparatus for high voltage parts in a hybrid electric vehicle. More particularly, the present disclosure relates to a fail-safe method and apparatus for high voltage parts in a hybrid electric vehicle, which enables the driving of high voltage parts so as to prevent the driving of the vehicle from becoming impossible due to inoperable high voltage parts.
(b) Background Art
In general hybrid vehicles, a power converter to charge a 12V battery and supply power to 12V electronic loads receives power of a high voltage battery as an input. Accordingly, when there is an abnormality in parts or controllers connected in parallel on a DC-link, a high voltage main relay for relaying a high voltage is turned off, and the power converter does not operate because the power converter cannot receive a normal high voltage input.
When the power converter does not normally operate in the event of an emergency, 12V-based electronic loads entirely consume power from a 12V battery. Accordingly, even though the discharging time varies with the degree of electronic loads, the battery is finally discharged to affect the normal running of a vehicle and thus threaten the safety of a driver.
In an abnormal situation involving a battery and an inverter, if a high voltage is not applied to the power converter, the power converter cannot perform its inherent roles of charging the battery and supplying power to the electronic loads. Accordingly, the electronic loads consume power only from the 12V battery.
When the discharging of the 12V battery occurs during the driving of a vehicle, vehicle controllers receiving power from the battery may stop operating. When the 12V battery is discharged below a certain voltage in an actual vehicle, the control power of the Motor Driven Power Steering (MDPS), which is typically sensitive to the battery discharging, is turned off, and thus the steering wheel is locked, threatening the safety of a driver.
Also, when the high voltage main relay is turned off, various high voltage parts, e.g., an electric oil pump, an air conditioner receiving power from the high voltage battery, etc., become inoperative. Particularly, since parts such as electric oil pumps are installed at a transmission, and cannot generate hydraulic pressure in the transmission when the electric oil pump does not operate, the driving of the vehicle may also be disabled.
In view of the above, Korean Patent No. 10-0877854 (hereinafter, referred to as Reference 1), filed and owned by the present applicant, discloses a method of driving a power converter of a hybrid vehicle in the event of an emergency. Reference 1 discloses a method of charging a 12V battery using an input of a counter electromotive force generated in a driving motor by dualizing a transmission map with respect to normal driving and emergent driving in which a high voltage main relay is turned off. However, this typical fail-safe method using the dualization of the transmission map provides an input high voltage of a power converter through the transmission map dualization when a main relay is turned off, and thus merely enables low voltage battery charging. Also, since there are limitations in stable voltage supply and low output voltage, the various parts using high voltage are difficult to stably drive.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the disclosure, and therefore, it may contain information that does not form the prior art that is already known to a person of ordinary skill in the art.